Caries-susceptible rats will be used in assay procedures which simulate human eating patterns, to evaluate the caries-producing ability of human foods and confectionery items, and to develop means to reduce the caries-producing ability of such items. A semi-purified, nutritious diet of moderate caries-producing ability is fed during a certain period or periods of each day to provide all nutrients in abundance, except calories. At another period or periods of each day, a test food item is fed alone in adequate amounts to supply the remaining caloric needs of the rats. The caries-producing ability of the test food item is considered to be proportional to the increase in caries activity above the baseline observed when only the nutritious diet is fed. The increase in caries activity caused when sucrose is offered as the standard test item is given a value of 1.0. The increase in caries activity observed when any other test food item is fed, with or without a caries-inhibiting supplement, is expressed as a ratio of the increase in caries activity for sugar. The test food item may be supplemented with various caries-inhibiting agents such as sodium trimetaphosphate to evaluate whether its caries-producing ability is reduced by the supplement. A series of experiments will be included in which sodium trimetaphosphate is evaluated to determine the lowest concentration and the shortest time of presence in the oral cavity at which caries inhibition is detectable. Other caries-inhibiting agents will be tested similarly. Evaluation will also be conducted on the influence on caries-producing ability of modifications in the gross composition and means of preparation of human foods.